During the operation of commercial or institutional kitchens, a significant amount of valuable heat energy is lost as a result of hot fumes being vented to the atmosphere. These hot fumes are generated from cook stoves, hot plates, deep fat fryers, and other cooking apparatus. As a result of the extreme heat and various fumes generated during cooking, it is necessary for the comfort and health of kitchen workers to exhaust these fumes on a continuous basis through flue chimneys or similar venting devices. This process effectively replaces the hot kitchen air with cooler, clean outside air. Although this circulation process is necessary to provide a constant source of clean air to the kitchen environment, this venting practice is both inefficient and uneconomical, especially in colder climates where the cost to heat internal air and water is significant.
A further problem encountered in commercial kitchens is the filtering of grease and other particulates entrained in the hot fumes generated during the cooking of foods. If improperly filtered, this grease can cause fouling and the eventual malfunction of air ventilation systems, as well as create fire hazards if allowed to accumulate. Accordingly, hot fume air filters, which are normally located in fume hoods over cooking surfaces, are generally required to be cleaned daily, or at a minimum of 2-3 times a week. This tedious cleaning process is both time consuming and expensive.
The use of heat exchangers to capture thermal energy above cooking surfaces has been known for years. These designs, however, position the heat exchangers substantially downstream of existing grease filters. This approach is unfavorable for at least three reasons. First, these designs are inefficient since the heat exchanger is located downstream of the grease filter and a significant distance from the heat source. Thus, valuable thermal energy is lost by absorption into the grease filter and through general dissipation prior to the heat reaching the exchanger. Second, the grease filters currently being used upstream of the heat exchangers impede air flow, especially when congested with grease, hence reducing the efficiency of the air ventilation system and heat transfer efficiency. Third, when the heat source is turned off, the grease quickly solidifies on the filters and requires cleaning for both safety and efficiency. Finally, despite the existence of these kinds of heat exchangers generally, many existing kitchens fail to incorporate any kind of heat exchanger. Retrofitting existing kitchen equipment with heat exchanger systems may require an entirely new flue hood assembly and substantial piping and accessories. This conversion is both time consuming and expensive.
Accordingly, it is the primary object of this invention to provide a substantially self cleaning filter which is capable of filtering grease and other particulate matter from hot vapors and fumes generated during the cooking of foods. It is the further object of this invention to transfer heat from the hot cooking fumes to a fluid passing internally through the filter. This fluid may in turn be used to heat air or water for a variety of subsequent uses. By combining the heat exchanger and grease filter into one integral component, the heat transfer of thermal energy is more efficient since the heat exchanger is located closer to the heat source and eliminates the heat dissipating effects of an upstream grease filter. Additionally, the fluid within the filter retains heat after the heat source is turned off, allowing the grease to melt and drain away, thus reducing the frequency of cleanings. Finally, this combined heat exchanger/filter is designed to replace existing grease filters, and thus be retrofitted easily and at low cost, without the need for new flue hood assemblies.